Before xerography, making copies of documents and books was primarily a manual process. Typesetting and carbon copies helped to automate this process somewhat for the creation of documents. However, copying already existing documents was done chiefly by hand.
The advent of xerography created a relatively inexpensive and automated means for making copies of existing documents. The first copiers were relatively slow (approximately 1 page per minute) and pages were manually fed. Today, a state of the art copier can produce copies at over 100 pages per minute. Additionally, document feeders, attached to the basic copier, allow users to copy great stacks of pages at a time automatically.
While copier speed has improved over time, current copiers employ fairly much the same technology used by their predecessors--light/lens copying. Essentially, a light/lens copier works by moving a scanning bar across the entirety of a page. The bar illuminates a portion of the page and its image is reflected and focused by an optical system of lens and mirrors to an image capturing device, such as photoreceptor. The image of the page is scanned line by line until the scanning bar has moved down the entire length of the page--usually by a system of wheels and pulleys.
While the traditional light/lens copiers work well for the reproduction of loose document pages, this type of copier does not work so well for the reproductions of bound pages, such as found in a book. Most conventional copiers still employ a fiat plate glass surface on which the document pages are positioned for image capture. In reproducing book pages, the book is opened to the pages of interest and held, face down, to allow the copier to capture the image. On a fiat plate, this process stresses the binding of a book over the course of repeated copying. This stressing is even greater if the user pushes down on the spine of the book to insure that the image is not distorted by the natural curvature of a book page at the point where it connects with the spine.
Attempts have been made to rectify the problem of undue stress by improving on the flat plate that accompanies the traditional light/lens copier. One such attempt is disclosed in Xerox Disclosure Journal, Volume 9, Number 6, at page 383, dated November/December 1984 by Vinod K. Agarwal and entitled "Book Copying Apparatus". Agarwal discloses the use of two platens that are joined together to form a "wedge" shape that allows the spine of the book to rest upon the corner of the wedge while the two opposite pages contact the surfaces of each respective platen. It is the shape of the wedge that reduces the amount of stress to the spine by allowing copies to be made of opposing pages without forcing the spine to be stretched beyond the angle defined by the wedge.
An exposure lamp is disposed adjacent to the corner of the wedge to illuminate both pages for reproduction. Opposing book pages are scanned in Agarwal's system by moving the exposure lamp first down the entirety of one opposing page and then down the other opposing page.
Another attempt is disclosed in laid-open German patent application number DE 35 45 404 A1, application date Dec. 31, 1985, laid-open date Jul. 2, 1987 by Hubert Pfreimter. Pfreimter improves upon the wedge concept for image reproduction. Essentially, Pfreimter uses an arrangement of movable mirrors to produce virtual images of opposing book pages. These virtual images may be projected simultaneously to some means of image capture not disclosed by Pfreimter.
Both Agarwal and Pfreimter require moving parts to create opposing page images. Agarwal requires a moving exposure lamp that creates reproductions in the traditional light/lens method. Pfreimter has an arrangement of moving mirrors that create simultaneous virtual images; but does not disclose a means for capturing these images onto an intermediate substrate. The motion of these mechanical parts represent the majority of the time spent in scanning opposing book pages. It is thus desirable to scan opposing pages simultaneously without the use of moving mechanical parts.
Recently, a faster method of image scanning and capture has been developed using fiat panel detectors. These detectors comprise an array of thin film transistors and sensors that function as pixel element detectors. These thin film elements are generally constructed over a translucent substrate such as glass, forming a two dimensional detecting surface. Such thin film arrays are disclosed in U.S. Pat. No. 5,017,989 issued on May 21, 1991 to Street et al and in U.S. Pat. No. 5,079,426 issued on Jan. 7, 1992 to Antonuk et al., both of which are herein incorporated by reference.
These fiat two-dimensional detectors have the unique property that they are able to capture an image without moving mechanical parts. Antonuk et a discloses an array structure that captures an images across all its pixel elements simultaneously. The image information is then read out by sequentially addressing each pixel. The exact structure and operation of the detector is described in greater detail in the above-mentioned patent and in context with the present invention below.
With the advent of these new image capturing devices, it is thus an object of the present invention to provide a book scanner that does not have moving, mechanical parts for the capture of opposing book page images.